[keltos01]

FLeet boat periscope :

notice the secondary vertical and horizontal lines forming across to the left and above the crosshairs.



http://www.fleetsubmarine.com/periscope.html

RL I-400 periscope :


http://www.webenet.net/~ftoon/memory/japsub.html

Here the secondary crosshair is not there
the vertical graduations do not match the horizontal line like on the US scope
there are 3 graduations under the horizontal line to be level with the vertical markers to the left, 4 on the US scope.


-> ergo different optics